Electrolytic cell



Oct. 15, 1935. A. GEORGIE'V I 2,017,835

I ELECTROLYTIC CELL Filed Dec. 25, 1930 amnion,

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Patented Oct. 15, 19 35 ELECTROLYTIC CELL Alexander Georgiev, Brooklyn, N. Y., assignor to Aerovox Corporation, Brooklyn, N. Y., a corporation of New York Application December 26, 1930, Serial No. 504,911

7 Claims.

My invention relates to methods for impregtnating and forming electrolytic cells, but finds a specialized field of usefulness in the formation of the films of the so-called dry type of electro- 45 lytic condensers and more especially for high voltage use, that is for use at tensions in excess of 500 volts.

An object of the invention is to assure the thor-' ough impregnation of the usual fibrous interlay between the closely correlated cathode and anode foils with the electrolyte from which the film on the anode is formed, and to perform this impregnation of the prebuilt or pre-wound completely dry condenser unit without resort to spe- V cial vacuum or pressure apparatus.

Another object is to form an electrolytic condenser of the foregoing type with a tough homogeneous film in large scale mass production, without the need for manually operated or controlled current-or voltage adjusting or regulating apparatus, without resort to delicate measuring instruments, and in fact by an entirely automatic operation.

A feature of the invention is the method of forming the pre-wound condenser section by impregnating the same in hot electrolyte, and then forming by applying direct current through a resistor in series with the condenser section, which is immersed throughout formation in a tray containing electrolyte of substantially the same composition as that used for the impregnation. Thus, as the dielectric film is formed and the ohmic resistance of the condenserincreases, the effective application of voltage rises in a direct proportion therewith, thereby insuring the formation of a uniform tough adherent filmon the anode foil.

This application is a continuation in part of my co-pending application Ser. No. 489,521, filed October 18, 1930 and issued Jan. 20, 1931, as Patent No. 1,789,949.

In the accompanying drawing, in which is shown one of various possiblev embodiments of the several features of the invention:

Fig. 1 is a plan view, indicating the method of forming,'and

Fig. 2 is a transverse sectional view on line 22 of Fig. 1 showing the forming arrangement. Referring to the drawing, the condenser unit, shown in outline at C, is preferably of the general type shown in my parent case, comprising superposed elongated cathode and anode foils with an interposed spacer comprising a layer of gauze or other liquid absorbent fabric. The anode foil has a tab t, unitary therewith, pmtruding from one edge thereof at the interior of 1 sections and their dimensions.

, is in turn connected in series with a correspondr In the forming the roll, and the'cathode has a tab t, unitary therewith, protruding from the opposite edge of, the roll at the exterior thereof. Preferably, the cathode presents one or more external convolutions forming a complete metallic enclosure serv- 5 ing as an electrostatic shield.

The condenser rolls, previously prepared according to conventional methods, areimpregnated by immersion in the usual type of impregnation tank charged with electrolyte which may be of any suitable composition but preferably comprises a mixture of glycerol and ammonium borate.

The hot electrolyte having high penetrabilityis readily seeped up in the absorbent gauze.

The condenser elements are then subjected to the forming operation, preferably by laying them in trays or pans ll of glass, aluminum or other material-unafiectedby the solution, filled preferably with liquid identical with the batch in the impregnation tank. Preferably the condenser terminals 15' and i are connected to releasable terminal clips l3 and M respectively mounted at opposite edgesof the tray and above the level of the liquid therein. Care is taken that the foil ill forming the electrostatic shield is connected to the negative terminal of the current source, to constitute the cathode. In series with the condensers, a few only of which are connected in parallel in each tray 2| is connected a resistor H preferably of about 2000 ohms more or less depending on the voltage, the number of Each resistor ing incandescent lamp L, the remaining terminal of which is connected to the positive terminal of the source of current G, which is preferably of a voltage slightly in excess of the peak voltage for which the condenser is to be adapted. The

trays as indicated in Fig. 1, may be conveniently 40 arranged in rows on racks or tables and all connected in parallel across the terminals of said source of forming current G. A closed circuit jack I B is disposed in each circuit, for ready connection of a milli-ammeter, for metering leakage current in ascertaining completion of the forming process. r

operation, the initial resistance of the immersed condenser roll is very lowsince I the currents flow only across athin film of conductive electrolyte of large areainterposed between the two condenser electrodes. The initial voltage across the condenser will be very small as practically the entire voltage drop will be across resistor R and lamp L. The small voltage on the condenser roll will form a very thin film upon the anode foil, the electrical resistance of which rises accordingly. Therefore, a larger proportion of the applied voltage will nowbe ap- 5 plied across the condenser foils, which brings about the formation of a greater thickness of film, resulting in the application of still higher voltage to the condenser. In this manner, the voltage applied across the condenser foils will gradually i and automatically increase as the formation of the dielectric film progresses, until, upon the Z completion of the forming operation, the resistance of the condenser will be vastly higher than that of theresistor R and practically all 15 of the voltage will be applied across the condenser terminals. This operation is continued until the voltage impressed across the condenser foils is slightly in excess of the peak voltage on which the condenser. is to be used. Where the i 20' peak voltage is 500, the forming voltage is pref-.

erably about 510.

With the arrangement above described, the lamp L serves to give visual indicationwhen the forming process is about completed. At the be- 25 ginning of the forming operation, and while it is in progress, the voltage applied to the lamp will be sufllciently high for inc'andescence thereof, but as the formation proceeds and the resistance of the condenser dominates, the lamp will .become 30 dimmer due to theresulting reduction in voltage thereacross and finally will be extinguished, The supervisor will thus be apprised of the substantial progress of the forming operation and thereafter, with the aid of the milli-ammeter applied 3 at the closed circuit lack it, he will know when the forming operation has been completed, at which time the condenser .roll is removed from the tray. The condenser roll thus formed, will have a dielectric film upon the anode of thick- 40 ness depending on the voltage and duration of forming operation, and the interlay will be soaked with the electrolyte liquid in contact with the film.

As shown in the drawing, only three or four 45 condenser sections are disposed in each tray, and

each tray has its individual resistor in series with the condensers themselves connected in parallel within the tray. Thus, should any one section fcrany reason fail to form, it is only those conso densers that are within the same tray the for-- matlon of which is hindered, and conversely...

should any one condenser withina tray sufier a breakdown during charging, it is only those condenser sections in the same tray that would tend to to discharge through the breaking down. This is to be distinguished from the difllculties ensuing should a multiplicityof condenser sections be placed in a common tank or tray with a common resistor.

60 From the foregoing method disclosed, it is seen that the film of eachcondenser section itself antomatically determines the impressed voltage accomplishing the continued forming of the film. By this'expedient, the need for rheostats or other as voltage or current adjusting apparatus is' dispensed with as is the need for skilled operation to conduct formation. The operation in ell'ect is entirely automatic. It follows as a necessary corollary from the foregoing operation that the plied voltage on each of the parallel connected condensers rises at the same rate as the forming pr, but the current is apportioned among the severalcondensers in such manner as to compensate for inequalities in the inherent rate of 7 formation. r

It has been found in experience, especially with the high voltage condensers, 500 to 600 volts or more, that the best results are accomplished by causing the voltage applied across the terminal to rise gradually and continuously without sudden increase, however small, such rise of voltage being determined by'the resistance of the forming film. This is ideally accomplished by the method above set forth. In this connection, it is to be noted that a sudden increase'of voltage, 10 however small, tends to break down the film formed" at the lower voltage, so that, such formation would not only be ineiilcient in eflecting alternations of film forming and breaking down but the resulting film would, by reason of such alternations, have a mechanically weak and'fiaky character. In applicant's case, the film is tough, homogeneous and durable. I

Having thus described my invention, what I claim as new and desire to secure by Letters Patcut is:--: r.

, l. The method'of forming an electrolytic condenser, .which consists in, submerging the completely wound section in hot electrolyte for thorough impregnation, then submerging the impregnated condenser section in a cooler body of electrolyte of substantially the same composition, as the impregnating electrolyte, and applying the forming current.

2. The method of forming in parallel a plul0 rality of substantially identical electrolytic condensers of the type involving closely superposed electrodes, which consists in submerging the completely wound condenser assemblies in an electrolyte of low aqueous content, applying di- 85 rect current voltage concurrently thereto and slowly and continuously increasing the voltage on each condenser assembly under control of the rising resistances of the forming di-electric films from the beginning until the formation is com- 40 pleted.

3. The method of forming in parallel a pinrality of electrolytic condensers of the type involving closelysuperposed electrodes, which consists in submerging the condenser assembly in an electrolyte of low aqueous content, applying direct current voltage thereto and slowly and continuously. increasing the voltage on each condenser assembly under control of the rising resistances of the forming di-electric films, and continuing said operation until the applied voltage is slightly in excess of the peak voltage at which the condenser is to be used.

4 The method of forming an electrolytic condenser, which consists in submerging the completely wound section in hot electrolyte for thorough impregnation, then submerging the impregnated condenser section in a cooler body of electrolyte of. substantially the same composition as the impregnating electrolyte,and applying direct current voltage thereto and slowly and continuously increasing said voltage with the rising resistance of the forming (ii-electric film.

5. The method of concurrently forming a plurality of substantially identical electrolytic con- .densers in parallel which consists in submerging the completely wound condenser assemblies in an electrolyte of low aqueous content, connecting a substantially constant electric resistance in series with said condenser sections and applying a constant source of potential across said series connected elements.

6. The method of formingin parallel a plurality of electrolytic condensers of the type involving two closely Buperposed electrodes with intervening spacers, which consists in incorporating electrolyte in said spacer means, connecting a source of direct current voltage across the two electrodes of the assembled condensers and slowly and continuously increasing the voltage on each assembly under control of the rising resistance of the forming di-electric films thereof, whereby the applied current will be automatically apportioned among the several condensers in such manner as to compensate for inequalities in the inherent rates of formation thereof and continuing said operation until the applied voltage exceeds the peak voltage at which the condenser is to be used.

7. The method of forming in parallel a plurality of electrolytic condensers of'the type involving two closely superposed electrodes with intervening spacer means, which consists in incorporating an electrolyte in said spacer means, connecting a single substantially constant electric resistance in series with the parallel connected completely wound condenser assemblies and connecting a constant source of potential across said series parallel connected elements wherebythe applied voltage on each condenser increases progressively with the forming, and the applied current is automatically apportioned among the several condensers in such manner as to compensate for inequalities in the inherent rates of formation thereof.

' ALEXANDER GEORGIEV. 

